Thin film transistor substrate, method of manufacturing the same, and display apparatus having the same

ABSTRACT

A thin film transistor substrate includes a thin film transistor including a gate electrode, a semiconductor layer, a source electrode and a drain electrode. Each of the source electrode and the drain electrode includes a wire layer and a protective layer. The protective layer includes zinc oxide in an amount greater than about 70% by weight and less than about 85% by weight and indium oxide in an amount greater than about 15% by weight and less than about 30% by weight.

This application claims priority to Korean Patent Application No.10-2014-0100615, filed on Aug. 5, 2014, and all the benefits accruingtherefrom under 35 U.S.C. §119, the contents of which are herebyincorporated by reference in its entirety.

BACKGROUND

1. Field

The invention relates to a thin film transistor substrate, a method ofmanufacturing the same, and a display apparatus having the same. Moreparticularly, the invention relates to a thin film transistor substratehaving improved electrical characteristics, a method of manufacturingthe thin film transistor substrate, and a display apparatus having thethin film transistor substrate.

2. Description of the Related Art

In general, a display apparatus includes a substrate, and pixelsarranged on the substrate. Each pixel includes a thin film transistorconnected to a gate line and a data line, which are each disposed on thesubstrate. The thin film transistor receives a gate-on voltage throughthe gate line and an image signal through the data line.

The thin film transistor is used as a switching device in the displayapparatus. A mobility of electric charges, which exerts influence onelectrical characteristics of the thin film transistor, is determineddepending on the state of a channel area of the thin film transistor,where charge carriers move through the channel area of the thin filmtransistor.

SUMMARY

One or more exemplary embodiment of the invention provides a thin filmtransistor substrate capable of reducing defects in a protective layerby improving deposition characteristics of the protective layer used tocover a thin film transistor.

One or more exemplary embodiment of the invention provides a method ofmanufacturing the thin film transistor substrate.

One or more exemplary embodiment of the invention provides a displayapparatus having the thin film transistor substrate.

Exemplary embodiments of the invention provide a display apparatusincluding a thin film transistor substrate, an opposite substrate facingthe thin film transistor substrate, and a liquid crystal layer betweenthe thin film transistor substrate and the opposite substrate.

The thin film transistor substrate includes a base substrate and a thinfilm transistor. The thin film transistor includes a gate electrode onthe base substrate, a semiconductor layer on the gate electrode andincluding an oxide semiconductor material, and an electrode layeroverlapping the semiconductor layer.

The oxide semiconductor material may include an oxide material of atleast one of zinc (Zn), indium (In), gallium (Ga) and tin (Sn).

The electrode layer includes a wire layer including a metal, aprotective layer on the wire layer, and a barrier layer under the wirelayer.

The metal included in the wire layer may include copper or a copperalloy.

The protective layer includes zinc oxide in an amount greater than about70 percent (%) by weight and less than about 85% by weight and indiumoxide in an amount greater than about 15% by weight and less than about30% by weight.

The barrier layer may be between the wire layer and the semiconductorlayer and may block diffusion of a material included in the wire layerto the semiconductor layer. The barrier layer may include at least oneof indium-zinc oxide, gallium-zinc oxide and aluminum-zinc oxide.

The electrode layer may include a source electrode and a drain electrodespaced apart from each other.

The display apparatus may further include a gate line and a data line,which are disposed on the base substrate. The gate line is elongated toextend in a first direction and is connected to the gate electrode. Thedata line is insulated from the gate line. The data line is elongated toextend in a second direction crossing the first direction and isconnected to the electrode layer.

Exemplary embodiments of the invention provide a method of manufacturinga thin film transistor substrate, including forming a gate electrode ofa thin film transistor on a base substrate, sequentially forming asemiconductor material layer, a barrier material layer, a metal materiallayer and a protective material layer on the base substrate and the gateelectrode, each of the material layers insulated from the gateelectrode, forming a first photoresist layer pattern on the protectivematerial layer on the base substrate and the gate electrode, selectivelyetching the semiconductor material layer, the barrier material layer,the metal material layer and the protective material layer using thefirst photoresist layer pattern as a mask to form a first structureincluding a semiconductor pattern, a barrier pattern, a wire pattern anda protective pattern, respectively, removing a portion of the firstphotoresist layer pattern on the semiconductor pattern, the barrierpattern, the wire pattern and the protective pattern to form a secondphotoresist layer pattern via which a portion of the first structure isexposed at a channel area of the thin film transistor, and etching thesemiconductor pattern, the barrier pattern, the wire pattern and theprotective pattern at the channel area of the thin film transistor usingthe second photoresist layer pattern as a mask to form a secondstructure including a semiconductor layer, a barrier layer, a wire layerand a protective layer of the thin film transistor, respectively.

The protective material layer includes zinc oxide in an amount greaterthan about 70% by weight and less than about 85% by weight and indiumoxide in an amount greater than about 15% by weight and less than about30% by weight.

The first structure may be formed using a first etchant that etches thesemiconductor material layer, the barrier material layer, the metalmaterial layer and the protective material layer.

The second structure may be formed using a second etchant that etchesthe semiconductor pattern, the barrier pattern, the wire pattern and theprotective pattern at the exposed portion of the first structure.

According to one or more exemplary embodiment, among elements of thethin film transistor, damage to the channel area, the source electrodeand the drain electrode thereof may be reduced or effectively prevented.Thus, the electrical characteristics of the thin film transistorsubstrate including the thin film transistor may be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other advantages of the disclosure will become readilyapparent by reference to the following detailed description whenconsidered in conjunction with the accompanying drawings wherein:

FIG. 1 is a perspective view showing an exemplary embodiment of adisplay apparatus according to the invention;

FIG. 2 is a plan view showing an exemplary embodiment of a pixelaccording to the invention;

FIG. 3 is a cross-sectional view taken along line I-I′ shown in FIG. 2;

FIGS. 4A to 4H are cross-sectional views showing an exemplary embodimentof a manufacturing method of a thin film transistor substrate accordingto the invention;

FIG. 5 is a scanning electron microscope (“SEM”) image showing anexemplary embodiment of a protective layer according to the invention;

FIG. 6 is an SEM image showing a first comparative example of aprotective layer; and

FIG. 7 is an SEM image showing a second comparative example of aprotective layer.

DETAILED DESCRIPTION

The invention now will be described more fully hereinafter withreference to the accompanying drawings, in which various embodiments areshown. This invention may, however, be embodied in many different forms,and should not be construed as limited to the embodiments set forthherein. Rather, these embodiments are provided so that this disclosurewill be thorough and complete, and will fully convey the scope of theinvention to those skilled in the art.

It will be understood that when an element or layer is referred to asbeing “on,” “connected to” or “coupled to” another element or layer, itcan be directly on, connected or coupled to the other element or layeror intervening elements or layers may be present. In contrast, when anelement is referred to as being “directly on,” “directly connected to”or “directly coupled to” another element or layer, there are nointervening elements or layers present. Like numbers refer to likeelements throughout. As used herein, the term “and/or” includes any andall combinations of one or more of the associated listed items.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, components, regions, layersand/or sections, these elements, components, regions, layers and/orsections should not be limited by these terms. These terms are only usedto distinguish one element, component, region, layer or section fromanother region, layer or section. Thus, a first element, component,region, layer or section discussed below could be termed a secondelement, component, region, layer or section without departing from theteachings of the invention.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the exemplary term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms, “a,” “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “includes”and/or “including”, when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

“About” or “approximately” as used herein is inclusive of the statedvalue and means within an acceptable range of deviation for theparticular value as determined by one of ordinary skill in the art,considering the measurement in question and the error associated withmeasurement of the particular quantity (i.e., the limitations of themeasurement system). For example, “about” can mean within one or morestandard deviations, or within ±30%, 20%, 10%, 5% of the stated value.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

Hereinafter, the invention will be explained in detail with reference tothe accompanying drawings.

FIG. 1 is a perspective view showing an exemplary embodiment of adisplay apparatus DP according to the invention.

Referring to FIG. 1, the display apparatus DP may be any of a number ofvarious display apparatuses, such as a liquid crystal display apparatus,an organic light emitting display apparatus, an electrophoretic displayapparatus, a microelectromechanical system display apparatus, etc. Inthe illustrated exemplary embodiment, the liquid crystal displayapparatus will be described as the display apparatus DP.

The display apparatus DP includes a thin film transistor substrate 100on which pixels PX are arranged and configured to display an image, anopposite substrate 200 facing the thin film transistor substrate 100,and a liquid crystal layer LC interposed between the thin filmtransistor substrate 100 and the opposite substrate 200.

The thin film transistor substrate 100 includes a display area DA inwhich the pixels PX are arranged and an image is displayed, and anon-display area NDA except for the display area DA. The non-displayarea NDA is disposed adjacent to the display area DA, and no image isdisplayed in the non-display area NDA. The opposite substrate 200 mayinclude a display area and a non-display area corresponding to those ofthe thin film transistor substrate 100. Pad circuits (not shown)electrically connect the thin film transistor substrate 100 to a drivingcircuit (not shown) that applies voltages to the pixels PX. The padcircuits are disposed in the non-display area NDA of the thin filmtransistor substrate 100.

The opposite substrate 200 is disposed on the thin film transistorsubstrate 100 and receives a voltage from an external source (notshown), the voltage from the external source being separate from thevoltages received by the thin film transistor substrate 100. However,according to another exemplary embodiment, the thin film transistorsubstrate 100 may receive two different voltages and the oppositesubstrate 200 may not receive any separate voltage.

The liquid crystal layer LC includes liquid crystal molecules havingdielectric anisotropy. When an electric field is formed between the thinfilm transistor substrate 100 and the opposite substrate 200, the liquidcrystal molecules are aligned in a specific direction relative to thethin film transistor substrate 100 and the opposite substrate 200, andthus the liquid crystal molecules control a transmittance of a lighttraveling through the liquid crystal layer LC. According to anotherexemplary embodiment, the liquid crystal molecules of the liquid crystallayer LC are driven in response to the two different voltages applied tothe thin film transistor substrate 100 to control the transmittance ofthe light.

FIG. 2 is a plan view showing an exemplary embodiment of a pixelaccording to the invention and FIG. 3 is a cross-sectional view takenalong line I-I′ shown in FIG. 2.

Referring to FIGS. 1 to 3, the thin film transistor substrate 100includes a first base substrate BS1, a data line DL, a gate line GL andthe pixel PX.

The first base substrate BS1 includes a transparent material such asglass or plastic. The gate line GL is elongated to extend in a firstdirection DR1, on the first base substrate BS1. The data line DL iselongated to extend in a second direction DR2 crossing the firstdirection DR1, on the first base substrate BS1. The gate line GL isinsulated from the data line DL while crossing the data line DL.

FIG. 2 shows one data line DL and one gate line GL, but each of the dataline DL and the gate line GL may be provided in a plural number withinthe display apparatus DP.

The pixel PX is connected to the gate line GL and the data line DL. Thepixel PX includes a thin film transistor TFT, and a pixel electrode PEconnected to the thin film transistor TFT.

The thin film transistor TFT includes a gate electrode GE, a sourceelectrode SE, a drain electrode DE and a semiconductor layer SL.

The gate electrode GE is protruded from a main portion of the gate lineGL to be elongated in the second direction DR2. The gate electrode GEand the gate line GL have a single-layer structure or a multi-layerstructure in a cross-sectional view. The gate electrode GE and the gateline GL are formed of the same material to include the same material andto be disposed in a same layer of the thin film transistor substrate 100among layers thereof on the first base substrate BS1.

The gate electrode GE includes at least one layer including a materialselected from an aluminum-based metal, such as aluminum (Al) or analuminum alloy, a silver-based metal, such as silver (Ag) or a silveralloy, a copper-based metal, such as copper (Cu) or a copper alloy, amolybdenum-based metal, such as molybdenum (Mo) or a molybdenum alloy,chromium (Cr), titanium (Ti), tantalum (Ta) and manganese (Mn).

The thin film transistor substrate 100 further includes a firstinsulating layer IL1 disposed on the first base substrate BS1 to coverthe gate electrode GE. The first insulating layer IL1 includes aninsulating material, e.g., silicon oxide (SiOx) or silicon nitride(SiNx).

The first insulating layer IL1 respectively insulates each of the sourceelectrode SE and the drain electrode DE from the gate electrode GE.Although not shown in figures, the gate line GL is insulated from thedata line DL by the first insulating layer IL1 disposed between the gateline GL and the data line DL.

The semiconductor layer SL is disposed on the first insulating layer IL1to partially overlap the gate electrode GE.

The semiconductor layer SL includes an oxide semiconductor material. Theoxide semiconductor material includes at least one oxide material fromamong zinc (Zn), indium (In), tin (Sn) and gallium (Ga). In an exemplaryembodiment, for instance, the semiconductor layer SL may include anindium-gallium-zinc oxide (“IGZO”), but should not be limited thereto orthereby.

The source electrode SE is protruded from a main portion of the dataline DL to be elongated in the first direction DR1.

The drain electrode DE is disposed to be spaced apart from the sourceelectrode SE. In the plan view, the source electrode SE and the drainelectrode DE are each overlapped with a portion of the semiconductorlayer SL.

The source electrode SE receives the data voltage through the data lineDL and the drain electrode DE receives the data voltage from the sourceelectrode SE via the semiconductor layer SL. The source electrode SE andthe drain electrode DE each include the same material as that of thedata line DL and have the same cross-sectional layer structure as thatof the data line DL. The source electrode SE, the drain electrode DE andthe data line DL are disposed in a same layer of the thin filmtransistor substrate 100 among layers thereof on the first basesubstrate BS1.

The source electrode SE and the drain electrode DE are disposed on thesemiconductor layer SL and expose a portion of the semiconductor layerSL. A channel area CA of the thin film transistor TFT is formed in theexposed portion of the semiconductor layer SL. The channel area CAserves as a path through which electric charges move. The data voltageapplied to the source electrode SE is applied to the drain electrode DEvia the channel area CA defined in the semiconductor layer SL.

The source electrode SE collectively includes a first barrier layer BL1,a first wire layer CL1 and a first protective layer PL1, which aresequentially stacked one on another. The drain electrode DE collectivelyincludes a second barrier layer BL2, a second wire layer CL2 and asecond protective layer PL2, which are sequentially stacked one onanother. That is, each of the source electrode SE and the drainelectrode DE has a triple-layer structure in the cross-sectional view.

The first and second wire layers CL1 and CL2 include the same materialand have the same layer structure. The first and second wire layers CL1and CL2 are disposed in a same layer of the thin film transistorsubstrate 100 among layers thereof on the first base substrate BS1. Indetail, each of the first and second wire layers CL1 and CL2 includes atleast one metal. In an exemplary embodiment, for instance, the first andsecond wire layers CL1 and CL2 include copper (Cu) or a copper alloy.

The first barrier layer BL1 is disposed between the first wire layer CL1and the semiconductor layer SL. The second barrier layer BL2 is disposedbetween the second wire layer CL2 and the semiconductor layer SL. Thefirst and second barrier layers BL1 and BL2 are disposed in a same layerof the thin film transistor substrate 100 among layers thereof on thefirst base substrate BS1.

The first and second barrier layers BL1 and BL2 reduce or effectivelyprevent the metal material included in the first and second wire layersCL1 and CL2 from being diffused to the semiconductor layer SL.

Each of the first and second barrier layers BL1 and BL2 includes atleast one material among vanadium (V), zirconium (Zr), tantalum (Ta),manganese (Mn), magnesium (Mg), chromium (Cr), molybdenum (Mo), cobalt(Co), niobium (Nb) and nickel (Ni). In addition, each of the first andsecond barrier layers BL1 and BL2 includes at least one metal oxide fromamong indium-zinc oxide (“IZO”), gallium-zinc oxide (“GZO”) andaluminum-zinc oxide (“AZO”).

The first protective layer PL1 is disposed on the first wire layer CL1to cover an upper surface of the first wire layer CL1. The secondprotective layer PL2 is disposed on the second wire layer CL2 to coveran upper surface of the second wire layer CL2. The first and secondprotective layers PL1 and PL2 are disposed in a same layer of the thinfilm transistor substrate 100 among layers thereof on the first basesubstrate BS1.

The first and second protective layers PL1 and PL2 reduce or effectivelyprevent the first and second wire layers CL1 and CL2 from making contactwith air, such that oxidation of the first and second wire layers CL1and CL2 is reduced or effectively prevented. Accordingly, deteriorationof electrical characteristics of the thin film transistor TFT due todenaturalization of the first and second wire layers CL1 and CL2 isreduced or effectively prevented.

Each of the first and second protective layers PL1 and PL2 includes themetal oxide. In the exemplary embodiment, each of the first and secondprotective layers PL1 and PL2 includes an indium oxide (“InO”) in anamount greater than about 15 percent (%) by weight and less than about30% by weight and includes a zinc oxide (“ZnO”) in an amount greaterthan about 70% by weight and less than about 85% by weight.

The thin film transistor substrate 100 according to the illustratedexemplary embodiment may further include a second insulating layer IL2disposed on the first insulating layer IL1 and on the source and drainelectrodes SE and DE. The second insulating layer IL2 includes aninsulating material, such as silicon oxide (SiOx) or silicon nitride(SiNx). The second insulating layer IL2 insulates the source electrodeSE and the drain electrode DE from other elements among those of thethin film transistor substrate 100 disposed on the first base substrateBS1.

The thin film transistor substrate 100 may further include an organicmaterial layer OL disposed on the second insulating layer IL2. Theorganic material layer OL planarizes an upper surface of the secondinsulating layer IL2 to provide a flat surface thereon.

The pixel electrode PE is disposed on the organic material layer OL. Acontact hole CH is defined in the organic material layer OL and thesecond insulating layer IL2 such as by etching, and a portion of anupper surface of the drain electrode DE is exposed via the contact holeCH. The pixel electrode PE is electrically connected to the thin filmtransistor TFT via the contact hole CH. The pixel electrode PE receivesthe data voltage through the second wire layer CL2 that serves as a partof the drain electrode DE.

The pixel electrode PE may be a transparent electrode. In an exemplaryembodiment, for instance, the pixel electrode PE includes a transparentconductive oxide, e.g., an indium-tin oxide (“ITO”), indium-zinc oxide(“IZO”), etc. Although not shown in figures, a plurality of slits may bedefined in the pixel PE.

Although not shown in figures, the thin film transistor substrate 100may further include a third insulating layer (not shown) disposed on(e.g., above) the organic material layer OL. The third insulating layercovers the pixel electrode PE.

In addition, the thin film transistor substrate 100 may further includean alignment layer (not shown) disposed on (e.g., above) the pixelelectrode PE. The alignment layer controls an alignment direction of theliquid crystal molecules of the liquid crystal layer LC.

The opposite substrate 200 includes a second base substrate BS2, a colorfilter CF disposed on the second base substrate BS2 to represent colors,a black matrix BM disposed around the color filter CF to block thelight, and a common electrode CE to form the electric field incooperation with the pixel electrode PE. The liquid crystal molecules ofthe liquid crystal layer LC are controlled by the electric field.

As described above, the common electrode CE, the color filter CF and theblack matrix BM are disposed in the opposite substrate 200, but shouldnot be limited thereto or thereby. That is, the common electrode CE maybe disposed in the thin film transistor substrate 100. Where the commonelectrode CE is disposed in the thin film transistor substrate 100, thecommon electrode CE is disposed on (e.g., above) or under the pixelelectrode PE in the cross-sectional view.

FIGS. 4A to 4H are cross-sectional views showing an exemplary embodimentof a manufacturing method of a thin film transistor substrate accordingto the invention. In FIGS. 4A to 4H, the same reference numerals denotethe same elements in FIGS. 1 to 3, and thus detailed descriptions of thesame elements will be omitted in order to avoid redundancy.

Referring to FIG. 4A, the gate electrode GE is formed on the first basesubstrate BS1. In forming the gate electrode GE on the first basesubstrate BS1, gate lines GL (refer to FIGS. 1 and 2) are substantiallysimultaneously formed with the gate electrode GE. The gate electrode GEand the gate lines GL are formed by forming a conductive material layerthrough a depositing or sputtering process and patterning the formedconductive material layer such as through a photolithography process,but should not be limited thereto or thereby.

Referring to FIGS. 4B and 4C, the first insulating layer IL1, asemiconductor material layer SML, a barrier material layer 10, a metalmaterial layer 20, a protective material layer 30 and a photoresistlayer PR are sequentially formed on the gate electrode GE and on thefirst base substrate BS1.

The first insulating layer IL1, the semiconductor material layer SML,the barrier material layer 10, the metal material layer 20 and theprotective material layer 30 are formed by a deposition or sputteringprocess. A photoresist layer PR is formed on the above-described layerssuch as by coating a liquid-form photoresist material on the protectivematerial layer 30. In the exemplary embodiment, the photoresist layer PRis formed of a positive-type photoresist material.

Then, a light is irradiated onto the photoresist layer PR on theabove-described layers such as through a mask MSK disposed above thephotoresist layer PR. The mask MSK may be a halftone mask or adiffraction mask and may include a first region R1 that blocks the lighttraveling thereto, a second region R2 that transmits a portion of thelight and blocks the other portion of the light traveling thereto, and athird region R3 that transmits the light traveling thereto. Only thelight that transmits through the mask MSK is irradiated onto thephotoresist layer PR. In irradiating the light onto the photoresistlayer PR, a portion thereof is removed such as at the second and thirdregions R2 and R3 to form a remaining portion thereof at the first andsecond regions R1 and R2.

The remaining portion of the photoresist layer PR from exposing theinitially formed photoresist layer PR to the light using the mask MSK isdeveloped to form a first photoresist layer pattern PR-P1. The firstphotoresist layer pattern PR-P1 is formed by completely removing thephotoresist layer PR in the third region R3. The exposure amount of thelight in the second region R2 is smaller than that in the third regionR3, and thus the remaining photoresist layer PR in the second region R2has a thickness smaller than a thickness of the remaining photoresistlayer PR in the first region R1.

Here, the photoresist layer PR is formed of the positive-typephotoresist, but should not be limited to the positive-type photoresist.That is, the photoresist layer PR may be formed of a negative-typephotoresist. When the photoresist layer PR is formed of thenegative-type photoresist, the photoresist layer pattern is formed onlyin the region through which the light transmits.

Referring to FIG. 4D, a portion of the layers underlying the firstphotoresist layer pattern PR-P1, which is not covered by the firstphotoresist layer pattern PR-P1, is etched using a first etchant untilthe first insulating layer IL1 is exposed at areas excluding the firstphotoresist layer pattern PR-P1. During the etching process, the firstphotoresist layer pattern PR-P1 is used as a mask. When the portion ofthe layers underlying the first photoresist layer pattern PR-P1, whichis not covered by the first photoresist layer pattern PR-P1, is etched,a first structure P1 is formed of remaining portions of the underlyinglayers.

Due to the first etchant, the portion of the protective material layer30, the metal material layer 20, the barrier material layer 10 and thesemiconductor material layer SML are sequentially etched.

In the exemplary embodiment, the first etchant may include at least onefrom among a persulfate compound, an azole compound, a water-solubleamine compound, a phosphate compound, a chloride compound, an organicacid, a fluorine compound, a sulfonic acid compound and an inorganicacid.

Each of the semiconductor material layer SML, the barrier material layer10, the metal material layer 20 and the protective material layer 30 isetched by the first etchant to remove portions thereof. Accordingly, asemiconductor pattern SL-P, a barrier pattern 10-1, a wire pattern 20-1and a protective pattern 30-1 are formed.

The semiconductor pattern SL-P, the barrier pattern 10-1, the wirepattern 20-1 and the protective pattern 30-1 collectively form the firststructure P1.

Referring to FIG. 4E, the first photoresist layer pattern PR-P1 is ashedto form a second photoresist layer pattern PR-P2 as a remaining portionof the first photoresist layer pattern PR-P1. The first photoresistlayer pattern PR-P1 is etched from an upper surface thereof at a uniformetch rate.

Referring to the different thickness portions of the first photoresistlayer pattern PR-P1 in FIGS. 4C and 4D, a portion of the firstphotoresist layer pattern PR-P1, which has a thickness smaller than thatof a remaining portion of the first photoresist layer pattern PR-P1, iscompletely removed by the ashing the first photoresist layer patternPR-P1 to form the second photoresist layer pattern PR-P2. As a result, afirst opening OP1 is defined by portions of the second photoresist layerpattern PR-P2, and a portion of the first structure P1, which isoverlapped with the gate electrode GE, is exposed via the first openingOP1.

Referring to FIG. 4F, the first structure P1 is etched using the secondphotoresist layer pattern PR-P2 as a mask to form a second structure P2.

The second structure P2 is formed by etching the portion of the firststructure P1, which is exposed through the second photoresist layerpattern PR-P2, using a second etchant. In etching the portion of thefirst structure P1, which is exposed through the second photoresistlayer pattern PR-P2, a second opening OP2 is formed via the secondstructure P2 in the area corresponding to the first opening OP1.

In the exemplary embodiment, the second etchant may include at least onefrom among the persulfate compound, the azole compound, thewater-soluble amine compound, the phosphate compound, the chloridecompound, and the organic acid. In particular, the second etchantincludes about 0.1% to about 20% by weight of the persulfate compound,about 0.01% to about 2% by weight of azole compound, about 0.1% to about10% by weight of water-soluble amine compound, about 0.1% to about 5% byweight of phosphate compound, about 0.001% to about 1% by weight ofchloride compound, about 0.1% to about 20% by weight of organic acid,and an amount of water that allows a total content of the second etchantto become 100% by weight.

The persulfate compound may include potassium persulfate (K2S2O8),sodium persulfate (Na2S2O8) or ammonium persulfate ((NH4)2S2O8). Theseare individually or jointly used.

The azole compound includes benzotriazole, aminotetrazole,aminotetrazole potassium salt, imidazole or pyrazole. These areindividually or jointly used.

The water-soluble amine compound includes glycine, iminodiacetic acid,lysine, threonine, serine, asparaginic acid, parahydroxyphenyl glycine,dihydroxyethyl glycine, alanine, anthranilic acid, tryptophan, sulfamicacid, cyclohexylsulfamic acid, aliphatic amine sulfonic acid, taurine,aliphatic amine sulfinic acid or aminoethanesulfinic acid. These areindividually or jointly used.

The phosphate compound includes NaH₂PO₄, Na₂HPO₄, Na₃PO₄, (NH₄)H₂PO₄,(NH₄)₂HPO₄, (NH₄)₃PO₄, KH₂PO₄, K₂HPO₄, K₃PO₄, Ca(H₂PO₄)₂, Ca₂HPO₄ orCa₃PO₄. These are individually or jointly used.

The chloride compound includes hydrochloric acid (HCl), ammoniumchloride (NH₄Cl), potassium chloride (KCl), iron chloride (FeCl₃),sodium chloride (NaCl), ammonium perchlorate (NH₄ClO₄), potassiumperchlorate (K₄ClO₄), sodium perchlorate (Na₄ClO₄) or zinc chloride(ZnCl₂). These are individually or jointly used.

The organic acid includes oxalic acid, oxalacetic acid, fumaric acid,malic acid, succinic acid, acetic acid, butyric acid, palmitic acid,tartaric acid, ascorbic acid, uric acid, sulfinic acid, tartaric acid,formic acid, citric acid, isocitric acid, α-ketoglutaric acid orglycolic acid. These are individually or jointly used.

The protective pattern 30-1, the wire pattern 20-1 and the barrierpattern 10-1 are etched by the second etchant.

The first and second protective layers PL1 and PL2 are formed by etchingthe protective pattern 30-1 using the second etchant. The first andsecond wire layers CL1 and CL2 are formed by etching the wire pattern20-1 using the second etchant. The first and second barrier layers BL1and BL2 are formed by etching the barrier pattern 10-1 using the secondetchant.

Accordingly, the source electrode SE includes the first protective layerPL1, the first wire layer CL1 and the first barrier layer BL1 is formed.In addition, the drain electrode DE includes the second protective layerPL2, the second wire layer CL2 and the second barrier layer BL2 isformed.

The semiconductor pattern SL-P is partially etched by the secondetchant, and thus the semiconductor layer SL is formed, in which thechannel area is defined.

The semiconductor layer SL, the source electrode SE and the drainelectrode DE collectively form the second structure P2.

Referring to FIG. 4G, the second photoresist layer pattern PR-P2 isremoved such as through an ashing process and/or a strip process.

After the second photoresist layer pattern PR-P2 is removed, apredetermined plasma gas (not shown) is supplied to an upper portion ofthe second structure. The plasma gas includes nitrogen oxide (NxO) oroxygen (O₂).

Referring to FIG. 4H, the second insulating layer IL2 and the organicmaterial layer OL are sequentially formed on the first insulating layerIL1 and the thin film transistor TFT.

The second insulating layer IL2 insulates the thin film transistor TFTfrom other elements among those of the thin film transistor substrate100 disposed on the first base substrate BS1 and reduces or effectivelyprevents infiltration of moisture of the organic material layer OL intothe thin film transistor TFT.

The organic material layer OL is formed such as by coating an organicmaterial on the first insulating layer IL1 and on the thin filmtransistor TFT, and drying the organic material. A flat surface of theorganic material layer OL provides a flat surface of the thin filmtransistor substrate 100.

A contact hole CH is formed extending through thicknesses of the organicmaterial layer OL and the second insulating layer IL2. The contact holeCH is formed in an area overlapped with the drain electrode DE.

The pixel electrode PE is formed on the organic material layer OL. Thepixel electrode PE is connected to the drain electrode DE via thecontact hole CH. The pixel electrode PE is formed such as by depositinga transparent conductive material on the organic material layer OL andpatterning the transparent conductive material.

In a method of manufacturing a display apparatus, the thin filmtransistor substrate 100 manufactured by the above-mentioned method iscoupled to an opposite substrate on which are defined elements such as acommon electrode, a color filter and a black matrix. The liquid crystallayer is interposed between the thin film transistor substrate and theopposite substrate.

As described above, the thin film transistor substrate is manufacturedby performing the photolithography process four times. Referring to FIG.4F, when the second structure P2 is formed using the second photoresistlayer pattern PR-P2 as the mask, sides of the first protective layer PL1are formed to have a taper angle that is the same as or similar to thatof the first wire layer CL1 and the first barrier layer BL1 with respectto the first base substrate BS1. In addition, sides of the secondprotective layer PL2 is formed to have a taper angle that is same as orsimilar to that of the second wire layer CL2 and the second barrierlayer BL2 with respect to the first base substrate BS1. The sides of thelayers within the source and drain electrodes SE and DE may coincidewith each other so as to be aligned with each other.

Hereinafter, an etch degree of the first and second protective layersPL1 and PL2 (hereinafter, collectively referred to as “protectivelayer”) according to a content of oxide materials included in theprotective layer will be described in detail with reference to thefollowing Table 1.

Table 1 shows the etch degree of the protective layer in which thecontent of the zinc oxide (ZnO) is different from the content of indiumoxide (InO).

In Table 1, the protective layer of each of an exemplary embodimentaccording to the invention, a first comparative example and a secondcomparative example is formed on a barrier layer and a wire layer, whichare sequentially stacked on the base substrate. The barrier layer andthe wire layer of each of the first and second comparative examples areformed under the same conditions as those of the barrier layer and thewire layer of the exemplary embodiment.

However, the content of the oxide materials included in the protectivelayer of each of the first and second comparative examples is differentfrom the content of the oxide materials included in the protective layerof the exemplary embodiment.

The protective layer according to the exemplary embodiment includesabout 80% by weight of zinc oxide and about 20% by weight of indiumoxide. The protective layer according to the first comparative exampleincludes about 70% by weight of zinc oxide and about 30% by weight ofindium oxide, and the protective layer according to the secondcomparative example includes about 85% by weight of zinc oxide and about15% by weight of indium oxide.

The etch degree of the barrier layer and the wire layer of each of theexemplary embodiment example, the first comparative example and thesecond comparative example is uniform with respect to the secondetchant, but the etch degree of the protective layer of each of theexemplary embodiment, the first comparative example, and the secondcomparative example is non-uniform with respect to the second etchant.

TABLE 1 First Second Exemplary comparative comparative embodimentexample example Zinc 80% by weight 70% by weight 85% by weightoxide(ZnO)content Indium 20% by weight 30% by weight 15% by weightoxide(InO)content Degree of etch of No variation Protrusion Recessprotective layer (0.07 ± 0.01 μm) (0.05 ± 0.03 μm)

In Table 1, the etch degree is determined by checking whether theprotective layer formed by etching the protective pattern (refer to 30-1in FIG. 4D) is protruded or recessed from the tapered side of the wirelayer and the barrier layer.

As shown in Table 1, the etch degree of the protective layer becomesdifferent depending on the content of the zinc oxide (ZnO) and theindium oxide (InO) therein.

FIG. 5 is an SEM image showing the protective layer according to theexemplary embodiment of the invention, FIG. 6 is an SEM image showingthe protective layer according to the first comparative example, andFIG. 7 is an SEM image showing the protective layer according to thesecond comparative example.

Referring to FIG. 5, the protective layer according to the exemplaryembodiment is etched to have sides at the same angle as those of thewire layer and the barrier layer, which are disposed under theprotective layer. As indicated by a dotted-line circle in FIG. 5, theside surface of the protective layer is inclined at the same angle asthat of the side surface of the wire layer and the barrier layer, andthe inclined surface of the protective layer is located at the samesurface as (e.g., coincides or aligns with) the inclined surfaces of thewire layer and the barrier layer, which are formed under the protectivelayer.

Referring to FIG. 6, the protective layer according to the firstcomparative example is less etched than the wire layer and the barrierlayer, which are disposed under the protective layer of the firstcomparative example. As indicated by a dotted-line circle in FIG. 6, theside surface, i.e., the inclined surface, of the protective layeraccording to the first comparative example is protruded in a lateraldirection with respect to the side surface, i.e., the inclined surface,of the wire layer and the barrier layer of the first comparativeexample.

Referring to FIG. 7, the protective layer according to the secondcomparative example is more etched than the wire layer and the barrierlayer, which are disposed under the protective layer of the secondcomparative example. As indicated by a dotted-line circle in FIG. 7, theside surface, i.e., the inclined surface, of the protective layeraccording to the second comparative example is recessed in a lateraldirection with respect to the side surface, i.e., the inclined surface,of the wire layer and the barrier layer of the second comparativeexample.

Where an insulating layer above the protective layer or the protectivelayer deposited on the metal material layer and protruded or recessedsimilar to the structures in the first and second comparative examples,a crack occurs in the insulating layer or the protective layer.

However, when the protective layer, which includes zinc oxide in anamount greater than about 70% by weight and less than about 85% byweight and indium oxide in an amount greater than about 15% by weightand less than about 30% by weight, is etched using the second etchantdisclosed herein, the protective layer may be formed without theprotrusion or the recess described above. As a result, the crack in theinsulating layer may be reduced or effectively prevented even though theinsulating layer is formed on (e.g., above or after) the protectivelayer. That is, deposition characteristics of the insulating layerdisposed above the protective layer and covering the thin filmtransistor are improved and defects in the insulating layer are reduced.Thus, the electrical characteristics of the thin film transistorsubstrate may be improved.

Although exemplary embodiments of the invention have been described, itis understood that the invention should not be limited to theseexemplary embodiments but various changes and modifications can be madeby one ordinary skilled in the art within the spirit and scope of theinvention as hereinafter claimed.

What is claimed is:
 1. A thin film transistor substrate comprising: abase substrate; and a thin film transistor on the base substrate, thethin film transistor comprising: a gate electrode on the base substrate;a semiconductor layer on the gate electrode; a source electrodeoverlapping the semiconductor layer; and a drain electrode overlappingthe semiconductor layer and spaced apart from the source electrode, eachof the source electrode and the drain electrode comprising: a wire layercomprising a metal; and a protective layer on the wire layer, whereinthe protective layer comprises zinc oxide in an amount greater thanabout 70% by weight and less than about 85% by weight and indium oxidein an amount greater than about 15% by weight and less than about 30% byweight.
 2. The thin film transistor substrate of claim 1, wherein thesemiconductor layer comprises an oxide semiconductor.
 3. The thin filmtransistor substrate of claim 2, wherein the metal comprises copper or acopper alloy.
 4. The thin film transistor substrate of claim 1, whereineach of the source electrode and the drain electrode further comprises abarrier layer between the semiconductor layer and the wire layer, thebarrier layer blocking diffusion of a material included in the wirelayer to the semiconductor layer.
 5. The thin film transistor substrateof claim 4, wherein the barrier layer comprises at least one ofindium-zinc-oxide, gallium-zinc oxide and aluminum-zinc oxide.
 6. Adisplay apparatus comprising: a thin film transistor substrate; anopposite substrate facing the thin film transistor substrate; and aliquid crystal layer between the thin film transistor substrate and theopposite substrate, the thin film transistor substrate comprising: abase substrate; and a thin film transistor on the base substrate, thethin film transistor comprising: a gate electrode on the base substrate,a semiconductor layer on the gate electrode and comprising an oxidesemiconductor, and an electrode layer partially overlapping thesemiconductor layer, the electrode layer comprising: a wire layercomprising a metal; and a protective layer on the wire layer, whereinthe protective layer comprises zinc oxide in an amount greater thanabout 70% by weight and less than about 85% by weight and indium oxidein an amount greater than about 15% by weight and less than about 30% byweight.
 7. The display apparatus of claim 6, wherein the electrode layercomprises a source electrode and a drain electrode spaced apart fromeach other.
 8. The display apparatus of claim 7, wherein the electrodelayer further comprises a barrier layer between the wire layer and thesemiconductor layer, the barrier layer comprising at least one ofindium-zinc oxide, gallium-zinc oxide and aluminum-zinc oxide.
 9. Thedisplay apparatus of claim 6, further comprising: a gate line on thebase substrate, elongated in a first direction and connected to the gateelectrode; and a data line on the base substrate, elongated in a seconddirection crossing the first direction and connected to the electrodelayer.
 10. A method of manufacturing a thin film transistor substrate,comprising: forming a gate electrode of a thin film transistor on a basesubstrate; sequentially forming a semiconductor material layer, abarrier material layer, a metal material layer and a protective materiallayer on the base substrate and the gate electrode, each of the materiallayers on the base substrate and the gate electrode insulated from thegate electrode, the protective material layer comprising zinc oxide inan amount greater than about 70% by weight and less than about 85% byweight and indium oxide in an amount greater than about 15% by weightand less than about 30% by weight; forming a first photoresist layerpattern on the protective material layer on the base substrate and thegate electrode; selectively etching the semiconductor material layer,the barrier material layer, the metal material layer and the protectivematerial layer using the first photoresist layer pattern as a mask toform a first structure comprising a semiconductor pattern, a barrierpattern, a wire pattern and a protective pattern, respectively; removinga portion of the first photoresist layer pattern on the semiconductorpattern, the barrier pattern, the wire pattern and the protectivepattern to form a second photoresist layer pattern via which a portionof the first structure is exposed at a channel area of the thin filmtransistor; and etching the semiconductor pattern, the barrier pattern,the wire pattern and the protective pattern at the channel area of thethin film transistor using the second photoresist layer pattern as amask to form a second structure comprising a semiconductor layer, abarrier layer, a wire layer and a protective layer of the thin filmtransistor, respectively.
 11. The method of claim 10, wherein the firststructure is formed using a first etchant which etches the semiconductormaterial layer, the barrier material layer, the metal material layer andthe protective material layer.
 12. The method of claim 10, wherein thesecond structure is formed using a second etchant which etches thesemiconductor pattern, the barrier pattern, the wire pattern and theprotective pattern at the exposed portion of the first structure. 13.The method of claim 10, wherein the semiconductor layer comprises anoxide semiconductor material, the oxide semiconductor materialcomprising an oxide material of at least one of zinc (Zn), indium (In),gallium (Ga) and tin (Sn).
 14. The method of claim 10, wherein theetching the barrier material layer, the metal material layer and theprotective material layer using the first photoresist layer pattern asthe mask forms inclined sides of the barrier layer, the wire layer andthe protective layer of the thin film transistor, respectively, theinclined sides being aligned with each other.